It may seem like an unlikely starting point, but the Queen’s visit to Ireland in 2011 started a chain of events that culminated in a Brexit “war-gaming” unit being set up in the Department of the Taoiseach (John Walsh writes).

It was tasked with ensuring that Ireland had advanced contingency plans in place when the British electorate voted to leave the EU on June 23.

The first visit by a British monarch in 100 years during May 2011 cemented a normalisation in relations between two former foes. Anglo-Irish relations were put on a path towards ever closer economic and political co-operation. In 2012, Michael D Higgins, the president, made the first official visit to Buckingham Palace by an Irish head of state.